title: Targeted delivery of an antibody-mutant human endostatin fusion protein results in enhanced antitumor efficacy.
abstract: The antiangiogenic protein endostatin showed considerable preclinical antitumor activity, but limited efficacy in phase I/II trials. Prior studies using an anti-HER2 antibody-murine endostatin fusion showed enhanced antitumor activity compared to anti-HER2 antibody or endostatin given alone, or in combination. We have generated two anti-HER2 human endostatin fusion proteins by fusing either wild-type or a mutant human endostatin (huEndo-P125A) to the 3' end of a humanized anti-HER2 IgG3 antibody. Antitumor efficacy was examined in murine and human breast tumor models. HuEndo-P125A antibody fusion protein (αHER2-huEndo-P125A) inhibited VEGF and bFGF induced endothelial cell proliferation, and tube formation in vitro, more efficiently than endostatin alone, wild-type endostatin fusion protein (αHER2-huEndo), or parental anti-HER2 antibody (αHER2 IgG3). Wild-type and mutant human endostatin was rapidly cleared from serum in mice (T½(2) = 2.0-2.1 hours), whereas αHER2-huEndo fusion proteins had a significantly prolonged half-life (T½(2) = 40.7-57.5 hours). Treatment of SK-BR-3 breast cancer xenografts with anti-HER2 IgG3-huEndo-P125A fusion resulted in greater inhibition of tumor growth and improved survival, compared to treatment with either αHER2 IgG3 (P = 0.025), human endostatin (P = 0.034), or anti-HER2 IgG3-huEndo (P = 0.016). αHER2-huEndo-P125A specifically inhibited tumors expressing HER2 in mice simultaneously implanted with murine mammary tumor EMT6 cells and with EMT6 engineered to express HER2 antigen (EMT6-HER2). Targeting of endostatin using antibody fusion proteins could improve antitumor activity of either anti-HER2 antibody and/or endostatin and provides a versatile approach that could be applied to other tumor targets with alternative antibody specificities.
authors.affiliation: Department of Medicine, University of Miami School of Medicine and Sylvester Comprehensive Cancer Center, 1475 N.W. 12th Avenue (D8-4) Miami, FL 33136, USA. sshin@med.miami.edu
authors.forename: Seung-Uon
authors.initials: SU
authors.lastname: Shin
authors.forename: Hyun-Mi
authors.initials: HM
authors.lastname: Cho
authors.forename: Jaime
authors.initials: J
authors.lastname: Merchan
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Krisztina
authors.initials: K
authors.lastname: Kovacs
authors.forename: Yawu
authors.initials: Y
authors.lastname: Jing
authors.forename: Sundaram
authors.initials: S
authors.lastname: Ramakrishnan
authors.forename: Joseph D
authors.initials: JD
authors.lastname: Rosenblatt
mesh_terms: D019943:Amino Acid Substitution; D020533:Angiogenesis Inhibitors / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D019540:Area Under Curve; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D043169:Endostatins / Q000235:genetics / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011817:Rabbits; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D020533:Angiogenesis Inhibitors; D000906:Antibodies; D000970:Antineoplastic Agents; D043169:Endostatins; D050505:Mutant Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011993:Recombinant Fusion Proteins; C508053:ERBB2 protein, human